SEER is a large population-based cancer registry database produced and maintained under NCI funding. SEER is a well known and valuable resource for epidemiological research on guest ions of cancer incidence, treatment effectiveness and related matters. CD-ROM is a revolutionary data storage medium that makes it possible for personal computers to inexpensively process large databases (650 Mbytes/platter). In the phase I (feasibility) project, a prototype product was built using NCHS CD-ROM software to make SEER available on a pc. Nine sites tested the prototype version and several recommended that the phase II product(s) be designed to serve education in addition to research needs. For phase II we propose to complete and commercialize a version of the product with the following enhancements: (l) add additional databases (county level populations, National Cancer Mortality, non-SEER state cancer registry data, other), (2) add additional datatypes of SEER (extent of disease, radiation treatment, other), (3) develop new ability for user to analyze user input datasets in comparison with CDSEER datasets, and (4) develop an electronic textbook that will support the teaching of cancer epidemiology and use the other CDSEER resources.